The present invention generally relates to telephone network architectures and, in particular, to an enhanced application telephone network architecture in which xe2x80x9cenhancedxe2x80x9d voice grade trunks are ubiquitously provisioned to route selected calls through call control nodes enabled to selectively exercise control over those calls.
Use of the telephone as a social and business instrument has exponentially grown over the past 100 years. The widespread acceptance of the telephone and its uses have spurred industry to create many innovations to facilitate call completion and enhance telephone services. Today""s telephone user community is sophisticated in the use of telecommunications equipment and demands faster connections, more services and better integration with computer applications to assist in streamlining their business operations.
The Public Switched Telephone Network (PSTN) as evolved to a highly automated computer-controlled switched network which permits callers to place calls to practically anywhere in the world. In this document, use of the term PSTN is intended to refer to any intelligent switched telephone network.
Advanced Intelligent Networks (AIN) now play a significant role in call routing in the PSTN and number portability will dramatically increase database control of initial call routing. In AIN, standardized xe2x80x9ctriggersxe2x80x9d in the network switching nodes permit call requests to trigger database queries for seeking call routing information. After call routing information is returned from a queried database, the call is connected through the network using standard call processing procedures.
Although the AIN is a high-speed multifaceted network which provides a vast array of automated telephone services, service development in the AIN is channelled by the AIN call model. In the AIN, new service development is accomplished using Service Creation Environments to create service logic programs that are executed by Intelligent Service Control Points (ISCPs), which are databases that respond to switch queries initiated by the AIN triggers. In the AIN call model the opportunities for initiating routing decisions are essentially limited to the trigger points embedded in the network call processing logic. Although the services offered in the PSTN are constantly being expanded and enhanced, new services are now routinely developed within the context of the AIN call model.
One disadvantage of the AIN call model is that many calls are routinely completed through the network only to be blocked or re-routed to a new termination. Popular services such as call screening and call forwarding work in this way. Consequently, congested network circuits are unnecessarily reserved for calls that are never completed to the dialed number, or redundant circuits are used to complete calls forwarded to a termination at another switching office.
The computer communications industry and the telecommunications industries are beginning to merge, but there has always been a measure of difficulty with the integration of the two. The PSTN has been perceived by those in computer communications as a closed architecture, encouraging computer vendors to displace the PSTN by creating overlay networks which avoid capitalizing on any more than core PSTN functionality.
Call routing using an overlay network requires many additional connections to the PSTN for both access and egress. Besides, routing within the PSTN from overlay networks often leaves connections established in nodes that are redundant to the call path. In overlay networks where there are limited connection points to the PSTN, calls can be routed over significant distances even though a call may complete on a network switching node where it originated. To address this problem, the telephone industry has endorsed the solution of release link trunk functionality for subsequent routing or rerouting of calls. The release link trunk functionality can reside in either the PSTN or in an overlay network, but the release link feature can only reside within a network switching node. The release link feature permits data messaging, usually SS7 ISUP messaging, to release a call back to the call set-up point, where rerouting can be performed to redirect the call. This feature is in wide use in the telecommunications industry today. Although the release link feature resolves some of the problems associated with redundant connections in the call path, the fact that it is a switching node resident is a significant drawback. Switch development and differences in proprietary protocols limit the use and availability of release link features.
In order to overcome the drawback, the applicant""s co-pending U.S. patent application, Ser. No. 08/939,909 entitled METHOD AND APPARATUS FOR DYNAMICALLY ROUTING CALLS IN AN INTELLEGENT NETWORK, and filed on Sep. 29, 1997, which is incorporated herein by reference, discloses a method and apparatus for dynamically re-routing calls through the network without disconnection of the calling party in response to any predefined criteria. The re-routing is achieved using standard common channel signaling messages formulated at a call control node which is a virtual node in the switching plane and a physical node in the signaling plane of the network. A Virtual Switch Point (VSP) or Intelligent Signaling Transfer Point (ISTP) is used as the call control node and the calls are routed to the VSP or ISTP using dedicated trunk groups which may be loop-back ISUP trunks or inter-switch ISUP trunks. The calls are routed to the dedicated trunk groups using standard routing translation tables and methods.
The method and apparatus disclosed in the applicant""s co-pending United States patent application provides a new level of flexibility in call routing control that permits the rapid introduction of new services. However, in order to capitalize on the full potential of this new facility, it must be ubiquitously available in the network. Consequently, there exists a need for a switched telephone network which enables point of origin control for selected calls, enhanced application development and, if resources permit, point of origin control for all inter-switch calls.
It is an object of the invention to provide an enhanced application switched telephone network and a method of handling selected calls associated with services provided in the network which enables point of origin control of the selected calls.
Another object of the invention is to provide a method for controlling selected calls associated with special services provided in the enhanced application switched telephone network to alleviate congestion on network facilities.
It is a further object of the invention to provide an enhanced application network in which regular calls may be overflowed to enhanced trunks when regular trunks are all busy.
It is another object of the invention to provide an enhanced application network in which special service calls are selectively controlled by call control nodes in the network.
It is a further object of the invention to provide an enhanced application network in which call control nodes cooperate with intelligent peripherals to provide enhanced application services.
It is yet another object of the invention to provide an enhanced application network in which all high usage trunk groups are enhanced trunk groups associated with call control nodes.
It is yet a further object of the invention to provide an enhanced application network in which all trunk groups interconnecting local switching offices and tandem switching offices are enhanced trunk groups associated with call control nodes.
In accordance with one aspect of the invention, there is provided an enhanced application telephone network having switching offices connected by trunk groups and enabled to communicate over a common channel signaling network to exchange call control messages for calls handled by the trunk groups, comprising:
a call control node connected to the common channel signaling network and configured as a virtual node in a switching plane of the enhanced application telephone network; and
at least one enhanced trunk for handling selected calls connected to each local switching office, the call control node being a virtual switching node logically located between opposite ends of the enhanced trunk so that common channel signaling messages related to the selected calls are delivered to the call control node, and the call control node is thereby enabled to exercise control over the selected calls.
In accordance with another aspect of the invention, there is provided a method for controlling a selected call associated with special services provided in a switched telephone network wherein a caller dials a predetermined sequence of digits for one of the selected calls, comprising steps of:
routing the selected call from an originating switching office that serves the caller to a trunk member that is connected to the originating switching office, the trunk member logically terminating at a call control node that is connected to a common channel signaling is network of the switched telephone network;
receiving at the call control node a common channel signaling message from the originating switching office, the common channel signaling message being related to the selected call;
determining at the call control node if the selected call is associated with a special service using information in the common channel signaling message;
if the selected call is associated with a special service, determining a call treatment option for the call, else forwarding the common channel, signaling message to a switching office associated with an opposite end of the trunk member; and
controlling the selected call associated with the special service using at least one common channel signaling message sent to a switching office connected to an end of the trunk member.
In the enhanced application telephone network call control nodes are advantageously enabled to exercise control of selected calls before the calls are routed through the network. As a result, the proportion of call processing in the PSTN related to blocked or failed call attempts is significantly reduced. Redundant circuits used to route selected calls to an enhanced trunk for control by a call control node are also eliminated. Therefore, the telephone network operates more efficiently and congestion in the network is reduced. Moreover, the enhanced application network enables the provision of an unknown number of new services, as well as a more intelligent provision of known services in the network.
In the enhanced application network every local switching office is provided with at least one enhanced trunk. An enhanced trunk is a regular voice-grade ISUP trunk having an associated link set and route set that directs common channel signaling messages to a call control node when a call is routed to the enhanced trunk. The call control node is therefore enabled to exercise control over the call before the call is progressed beyond the local switching office. Call treatment and service enablement is limited only by applications deployed on the call control node. Service enablement is further enhanced by providing the call control node with a data interface that permits communication with intelligent peripherals, application servers or other service resources directly or indirectly integrated into the enhanced application telephone network Computer telephony integration is thereby enabled without network overlays or redundant circuit use.
In a fully developed enhanced application network all outbound trunks from each local switching office are enhanced trunks. Translation tables and call routing decisions in the local switching offices are therefore simplified and exclusion tables at the call control nodes enable rapid call processing to permit regular calls to be passed through the call control node without appreciable delay.
Traditionally, IP integration in telephone switches has been accomplished using separate data channels into each telephone exchange. Most switch vendors now provide an IP data connection that permits some level of call control. This approach requires a separate OSS system and procedure to control t he overlay data network. The present invention capitalizes on existing signalling (specifically SS7) and uses that existing SS7 network to perform control functions. An OSS system is not required because SS7 has one of the most comprehensive OSS systems available in the PSTN.